The present invention relates to a magnetic tape apparatus in which a bearing interposed between a pinch roller and a roller shaft has been improved.
One example of a related magnetic tape apparatus will be described referring to FIG. 4. A feed reel stand 2 is engaged with a feed reel in the tape cassette 1. A take-up reel stand 3 is engaged with a take-up reel in the tape cassette 1. A movable tape guide post 4 draws out a magnetic tape t from the tape cassette 1 and winds it around a head cylinder 5. Reference numerals 6, 7 and 8 denote an entire erasing head, an audio erasing head and an audio control head, respectively. Reference numerals 9, 10 and 11 denote a stationary tape guide post, a back tension post and a capstan roller, respectively. A pinch roller 12 is rotatably disposed at one end of a supporting arm 14 which is rotatable around a pivotal shaft 13. At the other end of the supporting arm 14 is provided a cam pin 15 which is movably engaged in a cam groove 16a of a rotary cam 16.
In the above described structure, in a recording or a reproducing mode, for example, the magnetic tape t is drawn out from the tape cassette 1 by means of the movable tape guide post 4 and wound around the head cylinder 5 as shown in the drawing. Then, by rotating the rotary cam 16 at a determined angle to swing the supporting arm 14, the pinch roller 12 is pressed against the capstan roller 11 together with the magnetic tape in between to rotatively drive the capstan roller 11 whereby the magnetic tape t is caused to run.
A first related bearing structure for the pinch roller 12 has been disclosed in Japanese Patent Publication No. 10-228692A. In this structure, as shown in FIG. 5, the pinch roller 12 is so provided as to enclose an upper small-diameter portion 18a of a roller shaft 18 which is projectingly provided at one end of the supporting arm 14 by way of a bearing 19. The bearing 19 is formed of a synthetic resin and consists of an inner cylindrical portion 19a, an outer cylindrical portion 19b which are concentrically overlaid leaving a determined space therebetween, and a thin walled connecting portion 19c which interconnects the cylindrical portions 19a and 19b integrally at their middle portions. The pinch roller 12 consists of a cylindrical sleeve 12a formed of metal, and an elastically deformable roller body 12b formed of rubber or the like and attached to an outer peripheral face of the sleeve 12a. In FIG. 5, 21 denotes a washer, and 22 and 23 denote retaining members.
In the above described structure, when the pinch roller 12 is pressed against the capstan roller 11 together with the magnetic tape t in between, an inclination from a paralleled state of an axis O2 of the pinch roller 12 with respect to an axis O1 of the capstan roller 11 is so adapted to be absorbed by a clearance C between the bearing 19 and the roller shaft 18 and also by a so-called automatic centering function through elastic deformation of the bearing 19.
In the above described structure, because the outer peripheral face of the outer cylindrical portion 19b composing the bearing 19 is tightly fitted to an inner face of the sleeve 12a over the entire face, it has been difficult and annoying to insert the bearing 19 into the sleeve 12a. 
Moreover, the thin walled connecting portion 19c is pressed inwardly by inserting the bearing 19 into the sleeve 12a, and a bearing bore 20 formed through the inner cylindrical portion 19a is shrunk in diameter at a middle portion of its inner peripheral face, which will change an inner diameter of the bearing bore 20. Therefore, when the pinch roller 12 is engaged with the small-diameter portion 18a of the roller shaft 18 by way of the bearing 19 which has thus changed in the inner diameter, there has been a fear that a large difference may be created in alignment between the axis O2 of the pinch roller 12 and the axis O1 of the capstan roller, and a reliable function of the automatic centering mechanism may not be attained.
A second related art is disclosed in Japanese Patent Publication No. 10-172202A. In this structure, as shown in FIG. 6, the connecting portion 19c is positioned between the lower ends of the inner and the outer cylindrical portions 19a, 19b, and a large-diameter portion 20a is formed at a lower end of the bearing bore 20 so as to face with the connecting portion 19c. 
The above described structure has had such an advantage that even though the thin walled connecting portion 19c is pressed inwardly by inserting the bearing 19 into the sleeve 12a and the bearing bore 20 is partially shrunk in diameter at the inner peripheral face thereof, the shrinkage will be absorbed by the large-diameter portion 20a. However, there has been a fear that the connecting portion 19c may be worn out in a relatively short period since a pressing force of the pinch roller 12 is concentrically applied to the connecting portion 19c. 
In view of the above described problems, it is an object of the present invention to provide a magnetic tape apparatus in which a bearing can be easily inserted into a pinch roller, an automatic centering function can be fully exerted, and a life of the bearing can be maintained for a long period.
In order to achieve the above objects, according to the present invention, there is provided a magnetic tape apparatus comprising:
a capstan roller; and
a pinch roller for driving a magnetic tape loaded in the magnetic tape apparatus together with the capstan roller, including:
a tubular roller member, an outer periphery of which is to be abutted against the capstan roller by way of the magnetic tape;
a tubular bearing member provided inside of the roller shaft, the bearing member made of a resin material, and having a groove portion formed on a longitudinal center portion of an outer periphery thereof so as to form flange portions abutting against an inner periphery of the roller member in both longitudinal sides of the groove portion; and
a roller shaft provided inside of the bearing member.
According to the above described structure, the outer peripheral face of the bearing member is only partially fitted to the inner face of the roller member. Accordingly, the bearing member can be easily inserted into the roller member with a smaller force. Further, since the pressing force from the roller member is dispersively exerted on a pair of the flange portions, the pressing force will not damage the flange portions, and the life of the bearing can be maintained for a long period.
Preferably, the diameter of portions of the inner periphery of the bearing member where oppose to the flange portions are enlarged than the diameter of a portion where opposes to the groove portion.
According to the above described structure, since only the middle portion of the inner periphery of the bearing member is brought into contact with the roller shaft, and thereby a width of the portion in contact is small, the so-called automatic centering function can be fully exerted.
Preferably, the enlarged portions of the inner periphery of the bearing member are tapered faces formed so as to gradually enlarged outward.
According to the above described structure, the opposite ends of the inner periphery of the bearing member will not interfere with the roller shaft and will not do harm to the automatic centering function, even in case where the pinch roller is inclined to a relatively large extent.
Preferably, a width of each enlarged portion of the inner periphery of the bearing member in the longitudinal direction thereof is wider than a width of each flange portion in the longitudinal direction of the bearing member.
According to the above described structure, when the bearing member is inserted into the roller member, inward pressing forces are exerted on the flange portions and the opposite ends of the inner periphery of the bearing member are partially shrunk in diameter. Since the shrinkage can be absorbed by the large-diameter portions having the larger width, an inner diameter at the middle of the inner periphery of the bearing member will not change. Thus, the alignment of the axis of the roller member which engages with the roller shaft by way of the bearing member with respect to the axis of the capstan roller can be maintained at a high degree, whereby the automatic centering function can be fully exerted.
Preferably, an outer periphery of one end face of the bearing member is tapered.
According to the above described structure, the bearing member can be easily inserted into the roller member by abutting the tapered portion against the inner periphery of the roller member.
Preferably, an identification mark is provided on the other end face of the bearing member.
According to the above described structure, because the direction of the bearing can be surely identified by means of the identification mark, the bearing member can be accurately inserted into the roller member without error.
Preferably, a resin injection hole formed on the other end face of the bearing member serves as the identification mark.
According to the above described structure, the manufacturing cost can be saved as compared with the case wherein the identification mark is separately formed.